004: Concurrent Bot + Human Fixes Conflict

Problem

Human-triggered (/fix-agent or workflow_dispatch) and bot-triggered (pull_request_review) fix agents share the same concurrency group (fullsend-fix-pr-N). The newer run cancels the older one, even when they address independent issues.

Observed (PR #7)

Human triggered fix for linter issues. 4 minutes later, review agent submitted CHANGES_REQUESTED, triggering a bot fix that cancelled the human fix. The two fixes were independent.

Proposed Fix

1. Separate concurrency groups by trigger type — fix-bot-pr-N vs fix-manual-pr-N
2. Rebase on push conflict — if git push fails because the other agent pushed first, git pull --rebase and retry
3. Conflict reporting — if rebase fails, post conflicting files and escalate to human